Speed-control system for electric motors.



No. 826,318. PATENTED JULY 17, 1906.

A. D. DU BOIS. SPEED CONTROL SYSTEM FOR ELECTRIC MOTORS.

APPLICATION FILED APK.8, 1905.

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@221 736255 65 frame/2Z0?- 97 i I zzarazzderflj/afi A. D. DU 1201s. SPEED CONTROL SYSTEM FOR ELECTRIC MOTORS.

APPLICATION FILED APR. 8, 1905.

PATENTED JULY 17, 1906.

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UNITED s'rA rEs l arnivr orrron.

ALEXAXDER D. DU BOIS, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLl XOIS.

I SPEED-CONTROLSYSTEM FOR ELECTRIC MOTORS.

- Specification of Letters Patent. I

Patented July 17,1906.-

Application filed April 3, 1905- Serial No. 254,451.

tems for Electric Motors, of which the following is a full, clear, concise, and exact description. a

My invention relates to speed-control sys- 'tems for electric motors of the type wherein variations of the field strength are utilized to vary the motor speed.

. .The invention has for its object to provide an arrangement wherebythe desired amount of field resistance to be inserted in the fieldci'rcuit through the agency of the motor-starting switch may be adjusted or fixed, inde pendently of said starting-switch.

It is generally known by all persons familiar with the art that a motor may have its speed increased by the insertion and decreased by the withdrawal of resistance in the field-circuit and that a motor should have its full field strength at the time of starting and during the initial acceleration in order that it may have its maximum torque when most needed and may be prevented from sparking, which occurs when the field is weak. It is very desirable that electric motors governed in this way, which are used for driving machines requiring variations in their speed for different classes of .work such, for example, as lathcs, boringmills, shapers, Sac-shall be equipped so that they may be frequently stopped for examining or measuring the work or for setting new work and may be again started and brought automatically to the same speed at which they were previously running without reuiring the operator each time to adjust the field resistance to obtain the speed at which the motor was running before it. was stopped. Furthermore, it is often desirable in certain classes of work to vary the speed of the motor while running by altering the adjustment of the field resistance without disturbing the starting switch or arm.

In accordance with myinvention I employ a starting-rlieost at comprising an armature starting resistance with its controlling-arm, together with a field resistance having a variable maximum value and capable o adjusa I ment independent of the arm controlling the starting resistance for determining the amount of field resistance to be inserted in the field-circuit in order to bring the motor up to the desired speed. I employ this same starting-arm to insert the predetermined field resistance into the field-circuit after the armature resistance has been cut out. In my system, therefore, when it is desired to run the motor at a certain speed for a particular class of work, it is only necessary to set or adjust the field resistance for that speedthat is, give itv a maximum value which can be inserted in the field-circuit by the startingarmand the motor may be started and stopped and brought up to the speed for operating the starting-arm without changing or interfering with the adjustment of the field resistance.

I will describe my invention by reference to the accompanying drawings, wherein- Figure 1 is a circuit diagram illustrating the preferred form of my invention, and Fig. 2 is a diagram of anotherforin thereof;

The same characters bf reference designate the same parts wherever they are shown.

Referring first to Fig. 1, the armature a of line-circuit, said bridge being controlled by the main switch I) and an auxiliary switch I). A starting resistance R is provided for the armature-circuit and comprises a series of ance, and a controlling lever or arm R, ada ted to sweep over said terminals. The fina terminal 0 is connectedwith one pole of the armature, and the controlling-arm R is connected with the portion of the conductor 2 leading to the line in the usual manner.

A field resistance R is associated with the motor, having a controlling. arm or handle It". The field-winding F of the motor is included. in a conductor 3, leading from a conductor 1, between the auxiliary switch I) and the armature c, to the first terminal contact of'the field-resistance R the controlling-handle R thereof being connected b conductor 4 with the,first contact-ter'mina of the armatureresistance, so that when the starting-arm is in contact with the first or any terminal of said armature resistance the field-winding is in a bridge 3 4 of conductors 1 2.

which the field resistance is set by simply the motor is included in a bridge 1 2 of they contact-terminals c 0, connected by resist- I The controlling-arm R ot the field resistance is adapted to be moved to vary the maximum value of the field resistance or to (i d d d are provided, adapted to be succes sively engagedby the-starting arm, the terminal d hem adapted to be engaged by the arm R be ore or at the instant it touches the first terminal 0 of the armature resistance and until it comes into contact with the final terminal 0, when all the armature resistance is out out. The contact d is connected by a conductor 5 with the first contact-terminal, of the field resistance, so that, while the starting-arm is in engagement with contact or segme t d the entire field resistance, no

matter'w at inay be the position of its arm R is short-circuited. The contacts d d (l are connected by conductors 6 7 8, res ectively, with different portions of' the fiel resistance, so that the same is divided up into sections e e e a Thus, assuming the arm R of the field resistance to be set atpoint 10 of section c after the starting-arm has traversed its contacts 0 to out out armature resistance and has reached. its final contact c,'it leaves the auxiliary contact or segment d and engages the next auxiliary contact d, open- 'in the shunt 5 to include the section e in the fie d-circuit and completing a shunt 6 about the remaining sections. As the arm continues itsmovement' it opens shunt 6 and closes and opens shunt 7 8 about the other portions or v sections of the field resistance until the 'pre determined amount thereof is included in the field-circuit.

Ipreferably jrovide a solenoid B for moving the control ing -arm R over the starting resistance, said solenoid being included in a bridge 9 of conductors 1 2, adapted to be closed by the auxiliary switch I). The arm R may be provided with the usual dashpot B.

The starting resistance and its controllin arm, together with the field resistance and its independent controlling-lever, constitute the motor-starting rheostat. i

The operation of the system illustrated in Fig, 1 is as follows: The attendant, desiring to run the motor at a speed suitable ticular class of work, after having starte dxthe motor inthe ordinary way by closing switches to the proper point-A 01 exam e,

sts the field resistance in; speed by turv mg the controlling-handle it" th reel to section c to bring the correct amount of resistance into the field-circuit, or, in other words, to fix the maximum fieldres'istarme value which the starting-armEohtrols. He then in a subsequent starting of his motor would only need to close the m in switch I) and auxiliary switch b, completing a circuit for the solenoid, which draws the controlling-arm it of the armature starting resistance slowly over its associated contacts, gradually cut ting out said armature resistance.- [is long as the controlling-arm is in contact with the se mental the field resistance shortcir culted by conductor 5, allowing the motor to start with. full field strength; but as soon the armature resistance is cut out'the controlling-arm R leaves the segment at and en gages contact (1, opening the short circuit 5 about the field resistance and including the portion or section 6 of the field resistance in the field-circuit. The arm while in engage-- ment with the contact (2 short-circuits the a remaining sections of the field resistance. As the arm continues 1t opens the short c r-,

cuit last closed and includes the sections 6 e' in the field-circuit, short-circuiting the remainder, until when it reaches the end of its journey it has included the entire field resistance in the field-circuit. The field resistance and its adjusting handle orarm being independent of the starting resistance and its-controlling-arm, motor may now be stopped and afterward brought up to s eed as often as desired by simply operating tr e starting-arm without l'nteriering with the arm R and varying the adjustment of the field resistance. In case it be desired to vary the speed of the motor while the same is running it would simply be necessary to operate the'arm R of the field resists: is without in any way disturbing the motorstarting switch or lever B.

' The system shown in Fig. 2 illustrates a modified form of the invention wherein the redetermined maximum field resistance is inserted at a single step in the field-circuit immediately upon the removal of the start? ing resistance from the armature-circuit. To this end I provide an arm f, normally maintained by a spring 7" in position to force an insulated ccntact-arm f carried thereby, int-s engagei to close 'a short circuit about the predetermined maximum field resistance. The arm f is adapted to be engaged lay-the startinglever B after it has cut the resist-- ance out and moved toforce its contact-arm f away from its anvil to open short cir cuit. When the controlling-lever H" is re turned to normal position, the arm f returns under the influence of spring to reestabit with a tern'ilnai reestablish the short circuit. The controlling-arm may, as in this form of this invention, be an ordinary manual switch member.

It will be noted that with my system it is impossible to start the motor on a weakened field, since when the motor is started the short circuit of the field resistance is always closed.

I claim 1. In a speed-control system for electric motors, the combination with amotor, of an armature starting resistance for the motor, a controlling-arm for said resistance, a field resistance for the motor having a variable maximum value, means for adjusting the maximum value of said resistance independent of the starting resistance arm, and means controlled by said arm for bringing the redeterminted maximum field resistance into the field-circuit.

2. In a system of motor control, the com bination with a motor, of a starting resistance therefor with its controlling-arm, a field resistance, -mea s independent of said controlling-arm for determining the amount of field resistance to be associated with the motorfield, and means controlled in the movement of saidcontrolling-arm for gradually bringing the redetermined resistance into the field-circuit, after the armature resistance is cut out.

3. In a system of motor control, the com bination with a motor, and a starting-rheostat for the motor comprising a starting resistance with its controlling or starting arm, a field resistance, a controlling-arm therefor adapted to be moved independently of the starting-arm to vary the maximum value of the field resistance, and means, controlled by said starting-arm after the starting resistance is cut out thereby, to bring into the fie d-circuit the predetermined field resistance.

4. In a speed-control system for electric motors, the combination with a motor and a circuit therefor, of a startingresistance for the armature-circuit of said motor, an arm for said resistance adapted when moved to cut the same out of the armature-circuit, a field resistance for the motor, acontact-arm be moved along the field 'termine the amount of said resistance to be and its controllingarm, means for moving said arm independent of said. starting-arm, adapted to resistance to deassoci'ated with the motor-field, and a short circuit of the field resistance completed by the said starting-arm, said short circuit being broken after said arm cuts out the armature resistance to bring the motor to the desired.

speed; whereby the motor is allowed to start with full field strength. and after reaching the desired speed, may be stopped and automatically brought to the same speed by operating said starting-arm, without interfering with the field-resistance controlling-arm. 5. In a speed-control system for electric motors, the combination with a mbtor and its circuit, and a starting-rheostat therefor comprising a starting resistance and a leverarm therefor adapted to cutthe same gradually out Of'CiI'CLHlD, a field resistance, and a contact-arm therefor adapted to be moved to determine the amount of field resistance to be inserted in the field-circuit, said arm being at all times independent of the starting resistance arm, and shunts about different portions or sections of the field resistance controlled by the starting-arm in its move ment, to bring'th'e predeterminedfield-resistance gradually into the field-circuit after the armature resistance is cut out. l

6. In a speed-control system for electric motors, the combination with a motor and its circuit, of a starting resistance therefor electromagnetic to'control said resistance, a field resistance, means indeendent of the starting-resistance controling-arm for determining the amount of field resistance to be used, and. means controlled by said starting-arm, after the armature resistance is cut out, adapted to bring the predetermined field resistance into the fieldcircuit. i

In witness whereof I hereunto subscribe my name this 18th day of January, A. D. 1905.

- ALEXANDER D. DU BOIS.

Witnesses:

FREDERICK P. MoIN'rosH, E; F. BEAUBIEN. 

